Stalling after 100lbs

I had surgery on March 16, 2015 and I've lost 100lbs total (72 since surgery). Does the weight loss slow down for most after loosing the first 100 or might I be in a slight stall. My daily calorie intake is 800 and I walk 2 miles/4 days a week.

Sounds about right.  I was through my first 100 post op in less than four months.  The last sixty or so took another 7-8 months. 

That's what I've experienced also.  I lost my 100 in four months, and in the 3 1/2 months since I've lost 38.  It seems like every time I lose a pound or two, my body needs a few days to adjust before dropping anything else.